This extension is EXPERIMENTAL. The behaviour of this extension including the names of its functions and any other documentation surrounding this extension may change without notice in a future release of PHP. This extension should be used at your own risk.
Bcompiler was written for several reasons:
The second of these goals is achieved using the bcompiler_write_header(), bcompiler_write_class(), bcompiler_write_footer(), bcompiler_read(), and bcompiler_load() functions. The bytecode files can be written as either uncompressed or plain. The bcompiler_load() reads a bzip compressed bytecode file, which tends to be 1/3 of the size of the original file.
To create EXE type files, bcompiler has to be used with a modified sapi file or a version of PHP which has been compiled as a shared library. In this scenario, bcompiler reads the compressed bytecode from the end of the exe file.
bcompiler can improve performance by about 30% when used with uncompressed bytecodes only. But keep in mind that uncompressed bytecode can be up to 5 times larger than the original source code. Using bytecode compression can save your space, but decompression requires much more time than parsing a source. bcompiler also does not do any bytecode optimization, this could be added in the future...
In terms of code protection, it is safe to say that it would be impossible to recreate the exact source code that it was built from, and without the accompanying source code comments. It would effectively be useless to use the bcompiler bytecodes to recreate and modify a class. However it is possible to retrieve data from a bcompiled bytecode file - so don't put your private passwords or anything in it.